JPH0333452A - Fuel injection start timing control method for engine starting - Google Patents

Abstract

PURPOSE:To enhance the starting characteristic by gasifying the liquid fuel, mixing with air, and controlling the fuel injection start timing according to whether the combustion chamber temp. of an engine to make spark ignition is higher or lower than the specified value. CONSTITUTION:An electronic control device CPU 6 reads signals from an ignition switch 11, starter switch(SS) 12, and a temp. sensor 13. In accordance with the inflammation point of the fuel used and the temp. of the combustion chamber, the CPU 6 controls drive of a fuel injection valve 15 by reference to a control table 18 in which the injection start timing has been set. When the combustion chamber temp. is higher than the specific value, the injection valve 15 is driven at the same time as turning-on of a starter switch 12 so as to start the fuel injection. At the time of low temp., a throttle valve 16 is opened either fully or to the half depending upon the temp. when the starter switch 12 is turned on, and thus the compression ratio is enlarged, and the combustion chamber is heated. When the time set on a timer 14 is up, the fuel injection valve 15 is opened to make fuel injection. Thereby the low temp. starting characteristic is enhanced even with a fuel having a high inflammation point.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a starting fuel supply method used in spark ignition engines such as automobiles, outboard motors, portable power units, and consumer heat pump drive units. It is.

[Conventional technology]

Conventionally, for example, spark ignition engines in automobiles have used a vaporizer method in which fuel is sucked out with an air flow, atomized, and mixed with air, or a pressure-based method in which liquid fuel is pressurized and injected from a nozzle, atomized and mixed with air. Injection valve method is used,
The air-fuel mixture is transported to the combustion chamber using high-speed airflow, where it is ignited by a spark and combusted.

These air-fuel mixtures are a state in which atomized fuel particles are suspended in a high-speed air current, and some of the fuel is vaporized, but
Most of it adheres to the walls of the flow path and becomes liquid, and is sucked into the cylinder through the intake pipe while being pushed by the airflow, and along the way, it is vaporized by heat from the flow path wall surface or heat inside the cylinder. be done.

In this way, since most of the fuel is transported and vaporized in the wall flow, the injected fuel is not quickly transported to the cylinders, and the responsiveness and combustion efficiency of the engine are not necessarily sufficient.

In contrast, in the ultrasonic atomization device proposed by the applicant, fuel is almost completely atomized during injection and mixed with air, and this air-fuel mixture is efficiently transported into the cylinder by airflow. Therefore, it is possible to increase the combustion efficiency and increase the responsiveness of the engine by performing fuel injection in pulses and changing the injection frequency or duty.

[Problem to be solved by the invention]

By the way, exhaust emission (HC, Co) regulations for gasoline engines have become stricter in 2007, and attempts are being made to use methanol, ethanol, etc. as fuel. Methanol and ethanol are rated at 1f from an environmental standpoint, but their flash points are high at 11°C and 13°C, respectively, so if the engine is left for a long time, the combustion chamber temperature will drop below the flash point of these fuels. In such a case, the engine cannot be started, and even if an ultrasonic atomizer is used, low-temperature startability is poor.

The present invention is intended to solve the above-mentioned problems, and an object of the present invention is to provide a starting fuel injection start timing control method that can improve the low-temperature startability of an engine.

[Means to solve the problem]

The present invention is an engine driving method in which liquid fuel is vaporized, mixed with air, and ignited by a spark, and is characterized in that the fuel injection start timing is varied depending on whether the combustion chamber temperature is higher or lower than a predetermined temperature. When the combustion chamber temperature is lower than a predetermined temperature, the starter switch is turned ON with the throttle valve closed to start fuel injection after a predetermined time; when the temperature is particularly low, the throttle valve is opened with the ignition switch ON. , the fuel injection is started at the same time as the throttle valve is closed after a predetermined time.

[Effect]

The present invention varies the fuel injection start timing depending on the combustion chamber temperature at the time of startup, does not inject fuel for a predetermined period of time during low temperature startup, and starts fuel injection after raising the combustion chamber temperature by the compression heat generated by the starter drive. , it is possible to improve low-temperature startability even with a fuel having a high flash point. In addition, when the temperature is particularly low, the throttle valve is opened and the starter is driven to increase the compression ratio and heat the engine, thereby similarly improving low-temperature startability.

〔Example〕

The present invention will be described in detail below using an ultrasonic atomizer as an example, but the present invention is also applicable to other types of fuel injection systems such as pressure injection valve systems and carburetor systems.

FIG. 1 is a diagram showing the configuration of an ultrasonic atomization device, and FIG. 2 is a diagram for explaining the present invention in detail.

As shown in FIG. 1, the ultrasonic atomization device l includes an electrostrictive element 2,
Consisting of a horn 3 and a sleeve 4, the electrostrictive element 2 is driven by an alternating current voltage by an oscillator 7 controlled by an electronic control device 6 to vibrate in an ultrasonic frequency range, and this vibration is transmitted to the horn 3 and sleeve 3. .

On the other hand, liquid fuel from the fuel pump 8 is supplied to the electronic control device 6
The fuel is intermittently supplied from the injector 5 whose valve 5s is controlled to open and close, and is supplied to the horn 3 through the fuel passage 4a of the sleeve 4.
sprayed onto the surface. The injected fuel flows downward as a liquid film 9 on the surface of the horn 3, and is sprayed in the form of droplets at the tip due to the ultrasonic vibrations of the horn 3.

In the present invention, when injecting fuel, the fuel injection start timing is varied depending on whether the combustion chamber temperature at the time of startup is high or low, and when the temperature is low, the starter switch is turned on and fuel injection is started after a predetermined time. ing.

When the starter switch is turned on and the starter motor drives the engine, the combustion chamber is heated by compression heat and cooled by adiabatic expansion, but the compression heat is transferred to the cylinder wall and the temperature of the combustion chamber rises, causing a thermocouple. When the atmospheric temperature in the combustion chamber is detected, it rises while changing in a zigzag pattern according to compression and expansion, as shown in FIG. The way this temperature rises varies depending on the compression ratio; for example, as shown in Figure 3, when the throttle valve is fully open, the temperature rises with a curve like the broken line in the figure, and when the throttle valve is closed, it rises with a curve like the solid line in the figure. .

Therefore, in the present invention, when the temperature is high and it is easy to start, fuel injection is started at the same time as the starter switch is turned on, as in the conventional case, and when the temperature is low, compression heating is performed with the throttle valve closed, and fuel injection is performed after a predetermined period of time has elapsed. start,
Furthermore, when the temperature is particularly low, the throttle valve is fully opened to perform compression heating, and after a predetermined time, the throttle valve is closed and fuel injection is started at the same time, thereby improving startability.

FIG. 4 is a time chart particularly for starting at low temperatures.

As shown in the figure, fully open the throttle valve at the same time as the ignition switch is turned on. The starter switch 12 operates the starter motor circuit to drive the starter motor, and at the same time a timer is set. The timer set value is appropriately set depending on the flash point of the fuel used. In this state, the intake amount of air is maximum, so the compression ratio is high, and the temperature of the combustion chamber rises according to the curve shown by the broken line in FIG. When the timer set time has elapsed, the throttle valve closes and the minimum amount of air necessary for combustion is sucked in through the bypass passage.

At the same time, the fuel injection valve circuit operates to start fuel injection. At this time, the temperature of the combustion chamber decreases somewhat due to the heat of vaporization of the fuel, but since the temperature of the combustion chamber has already risen to a predetermined temperature or higher, the engine is easily started and the starter motor is turned off.

In order to operate as described above, the injection start timing, which is set according to the flash point of the fuel and the combustion chamber temperature at the time of startup, is mapped and created as a control table, and this table is referenced at the time of startup to start fuel injection. Starting performance can be improved by controlling the timing.

FIG. 5 is a block diagram showing the configuration of a device for performing such fuel injection start timing control.

The electronic control device 6 reads signals from the ignition switch 11, starter switch 12, and temperature sensor 13, and controls the fuel by referring to the control table 18 in which the injection start timing is set according to the flash point of the fuel to be used and the combustion chamber temperature. The injection valve 15 is driven and controlled. If the combustion chamber temperature is higher than a predetermined temperature, the fuel injection valve 15 is driven at the same time as the starter switch is turned on to start fuel injection. When the temperature is low, the throttle valve 16 is fully opened or closed when the starter switch 12 is turned on depending on the temperature, and the compression ratio is changed depending on the temperature to heat the engine. When a timeout signal is received from the timer 14 after a predetermined period of time has elapsed, the fuel injection valve is driven to start fuel injection. In this way, by controlling the fuel injection start timing, startability can be improved.

Note that the present invention uses SPI (Single Possible Injection), which injects fuel near the carburetor and distributes fuel to each cylinder.
MP I (Multi Point Injector) system, which injects fuel near the intake valve.
It is applicable to either of the following methods.

〔Effect of the invention〕

As described above, according to the present invention, the fuel injection start timing is varied depending on the combustion chamber temperature at the time of startup, and the combustion chamber is heated by compression heat for a predetermined period of time without injecting combustion when the temperature is low.
Since fuel injection is started after a predetermined period of time has elapsed, it is possible to improve low-temperature startability even with fuel having a high flash point.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of the ultrasonic atomization device of the present invention, and FIG.
The figure is a diagram for explaining the control method of the present invention, Figure 3 is a diagram for explaining the temperature rise curve due to compression heating when the throttle valve is fully open and closed, and Figure 4 is a time chart of the injection start timing. The figure shown in FIG. 5 is a block diagram of a device configuration for implementing the control method of the present invention. 1...Super sound? J1 atomization device, 2... electrostrictive element, 3.
... Horn, 4 ... Sleeve, 5 ... Injector, 6 ... Electronic control device, 8 ... Fuel pump, 18
...control table.

Claims (3)

[Claims] (1) An engine driving method in which liquid fuel is vaporized, mixed with air, and ignited by a spark, during startup, characterized in that the fuel injection start timing is varied depending on whether the combustion chamber temperature is higher or lower than a predetermined temperature. Fuel injection start timing control method. (2) When the combustion chamber temperature is lower than a predetermined temperature, the starter switch is turned on with the throttle valve closed, and fuel injection is started after a predetermined time. Timing control method. (3) When the combustion chamber temperature is lower than a predetermined temperature, the throttle valve is opened by turning on the ignition switch, and fuel injection is started at the same time as the throttle valve is closed after a predetermined time. Injection start timing control method.